<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>呼吸灯</title>
    <style>
        *{
            box-sizing: border-box              /*怪异盒子*/
        }
        div.artical{
                width: 250px;
                height: 350px;
                background-color:black;
                margin:0 auto;
        }
        div.top{
            width: 250px;
            height: 250px;
            padding: 20px;
            animation-name: outer;
            animation-duration: 5s;
            animation-iteration-count: infinite;
            animation-timing-function: linear;
        }
        div.text{
            color: #ffffff;
            text-align: center;
        }
        div#outer{
            height: 100%;
            border: 5px solid #cccccc;
            border-radius: 50%;
            padding: 20px;
            animation-name: inner;
            animation-duration: 5s;
            animation-iteration-count: infinite;
            animation-timing-function: linear;
        }
        div#inner{
            height: 100%;
            border: 10px solid #ffffff;
            border-radius: 50%;
        }
        @keyframes outer{
            25%{
                padding: 10px;
            }
            50%{
                padding: 20px;
            }
            100%{
                padding: 20px;
            }
        }
        @keyframes inner{
            25%{
                padding: 30px;
            }
            50%{
                padding: 20px;
            }
            75%{
                padding: 32px;
            }
            100%{
                padding: 20px;
            }
        }
    </style>
</head>
<body>
    <div class="artical">
        <div class="top">
            <div id="outer">
                <div id="inner">

                </div>
            </div>
        </div>
        <div class="text">hi!!!!</div>
    </div>
</body>
</html>